Patent EP-2237100-A1 (EP)
Inventor: SHINOHARA TOSHIHIDE
IPC: G02C7/02
Filed: 2010-03-30
Abstract: A progressive power lens includes: a pair of an outer refractive surface and an inner refractive surface, at least one of the outer refractive surface and the inner refractive surface being a progressive surface, relationships as follows being defined with respect to a lens to be actually worn:    SV  =  SPH  +  CYL      cos   AX    2         Dm  ¢  1  =   N  -  1     Cm  ¢  1     
and    Dm  ¢  2  =   1  -  N     Cm  ¢  2     
where: SPH represents a spherical power; CYL represents a cylindrical power; AX represents a cylinder axis; ADD represents an addition power; N represents a refractive index of the lens; SV represents a vertical refractive power; Cm I represents a curvature of a cross-section of an outer surface taken along a main fixation line; Cm2 represents a curvature of a cross-section of an inner surface taken along the main fixation line; Dm1 represents a surface power of the cross-section of the outer surface taken long the main fixation line; Dm2 represents a surface power of the cross-section of the inner surface taken along the main fixation line; PA represents a pantoscopic angle, the angle being defined as positive when formed in a direction is which the lens is laid down; Y represents a vertical distance from a prism reference point, the distance being defined as positive when taken in an upper direction of the lens fitted in a frame; Yf represents a Y-coordinate of a point located on the main fixation line and within the vertical distance Y of 5<Y<15; and Yn represents a Y-coordinate of a point located on the main fixation line and within the vertical distance Y of -15<Y<-5, 
relationships as follows being defined with respect to a lens designed for a standard pantoscopic angle:    Dm  ¢  1  ¢  o  =   N  -  1     Cm  ¢  1  ¢  o     
and    Dm  ¢  2  ¢  o  =   1  -  N     Cm  ¢  2  ¢  o     
where: Cm1o represents a curvature of a cross-section of an outer surface taken along the main fixation line; Cm2o represents a curvature of a cross-section of an inner surface taken along the main fixation line; Dm1o represents a surface power of the cross-section of the outer surface taken along the main fixation line; Dm20 represents a surface power of the cross-section of the inner surface taken along the main fixation line; and PAo represents a pantoscopic angle defined as positive when formed in a direction in which the lens is laid down, 
relationships as follows being defined:    PA  =  PA  -  PAo     
and    Dm   Y   =   Dm  ¢  1   Y   +  Dm  ¢  2   Y    -   Dm  ¢  1  ¢  o   Y   +  Dm  ¢  2  ¢  o   Y       
where: PA represents a deviation of the pantoscopic angle between the pantoscopic angle of the lens to be actually worn and the standard pantoscopic angle; and Dm(Y) represents a difference between a sum of the surface powers of the cross-sections of the outer surface and the inner surface of the lens to be actually worn taken along the main fixation line and a sum of the surface powers of the cross-sections of the outer surface and the inner surface of the standard lens taken along the main fixation line, and 
relationships as follows being satisfied:    PA     0   and Dm   Yf      Dm   Yn